Telephone trunk circuits



1; WICKS.

TELEPHONE TRUNK CIRCUITS. APPLICATION FILED JUNEII, 1917.

1,41%435. Patented Apr. 11, 1922.

hn Mcks 5 4 a ZZLZFLU all men STATES "PATENT ornca- 'rnnnrnonn TRUNK Be it known that I, JoHN Wio Ks, a citiizen of the United States of Ameriea,'. and a resident of Chicago, county of Cook, and State of Illinois, have inventedcertainnew :in Telephone My invention relates in general to trunk circuits for telephone systems and more particularly to circuits of this character'which are adapted for use in automatic telephone.

. systems. More specifically, my "invention .two' way trunk circuit over which a branch exchange operator may complete connec- -may.also be used by in extending connect1ons' to the branch.

has forits object the provis on of'improvedj trung' circuits for connecting a main automatic exchange with isolated manual branch exchanges subsidiary thereto, and is espe-" cially useful in those caseswhere the branch exchanges are of small size and are located at considerable distance.

In carrying out my invention I provide a trons between local subscribers and sub-- scribers in' the main exchange; and which the latter subscribers eans-is provided for giving the operator I supervisiononthe former class of connections. The control-of the supervision and also the control of the automatic switches in the main exchange" 1sexerclsed over a simplex clrcultsuperimposed 1n the usual I manner on the talking conductors of the 'line trunk. The battery for the switch control circuit is preferably located at the branch exchange, as'less trouble is experienced from leakage in'this way, and I provide also means forcharging this battery from the main exchange during conversation.

-These and other desirable features of my invention will be explained fully hereinafter, reference being had to'the accompanying drawing, which shows diagrammatically .a "tw0 way trunk circuit embodying the princlples of my invention.

reference characters 15 two line conductors of In the drawing,

posite ends in the windings of the repeating coils R and R. At the branch exchange:

the trunk conductors 15 .and'16 areainducs tively connected through the medium of repeatlng coil R with thetip and ring springs of the jack J. ,Associated with the jack J ,n 'ncataamea a... 11

drawing, but they of the repeating coil established over the 301m wrcxs, or dmcxeo, xnrmorscassrenon '10 AUTOMATIC ELECTRIC COMPANY, orcnrcaeo, ILLINOIS, A CORPORATION or ILLINOIS.

cmctrrrs.

r relay 4: and a calling device key all of which are indlvldual to the jack J. There is also shown a calling device CD which may be of the general type ofcalling device discole'sd 1n the British Patentto Dicker No. 29654 there is'shown a drop 2 for incomin signals a supervisory'signal 3, a olarizef operator is, of-course, provided with a number of cord circuits for interconnecting local 'lines,wh1,ch may also be used for the pose of connecting circuit. -No cord I pura local line with a trunk circuit is shown in the will be'understood to be .ofnany. suitable'type, and'since magneto substations are generally used in isolated branch exchanges such as the one now under conslderation, they maybe comparatively simple in design.

a At the main exchange the truck conductors .15and 16 are inductively connected through the medium of repeating coil R with the conductors'30 and 31'which latter may terminate in an individual line switch of the type disclosed in the patent to Newforth No. 1,078,690, January 17, 1912,,reissued on April 13, 1915, as No. 13,901. The main exchange is assumed to be of the well known two wire type such as is described in the patent above mentioned. Just to the right R, there is shown a repeater comprising the relays 20 to 23, inclusive, whose functions will be described.

WhileI have shown throughout the drawing a plurality of batteries, there will be in practice but two principal batteries, one at the'main exchange and the other at the branch exchange. Thus batteries B, B, and B are one and. the same battery which is the regular central battery at the main exchange. The batteries B, B and B, at the branch exchange likewise may be a single battery, which may be composed of small storage cells or dry cells. In addition to the batteries mentioned, there is also provided at the main exchange, a booster battery which is indicated by the reference character B The manner in which connections are trunk circuit will now be explained. 1 For this purpose it will be assumed that-a'local subscriber in the branch exchange desires to obtainconnection with a subscriber in the main exchange and has of 1910. The calling device CD may be :common to a number of trunk circuits. The

signaled the operator in the usual manner.. The operator will therefore connect the line of the calling subscriber through the medium of one of her cord circuits with an idle trunk line extending to the main exchange. Assuming that the trunk line to be used 1s the one shown in the drawing, when the calling plug of the cord circuit is inserted in the ack J, the drop 2 is disconnected in an obvious manner, and at the same t1me a circuit for the relay 20 at the distant main exchange is completed as follows: ground at G, resting contact of upper armature of relay 23 and the said armature, winding of relay 20, lefthand windings of repeating coil R in parallel, conductors 15 and 16 1n parallel, righthand windings of repeating COIl R in parallel, contact springs 5 and 6, contact springs 7 and 8, winding of polarized relay 4, and the armature of the said rela and its resting contact to battery B. pon the closure of the above circuit, the polarlzed relay 4 is not operated. At the mam exchange, however, the relay 20 1s energized and completes an energizing-circuit for the 'slow act1ng relay 21. Upon attracting its armature, rela'y 21 completes a circult P through the upper wlnding of the electropolarized relay 22. The. upper windlng of relay 22 is of high resistance and few turns, being composed of German silver wire, and relay 22 therefore is not energized. When the relay 20 was energized, it also completed at its lower armature a conductive bridge across the conductors 30 and 31 which extends as follows: conductor 30, lower righthand winding of the repeating coil R, resistance 26, working contact of the lower armature of relay 20 and the said armature, lower winding of relay 22, and the upper righthand winding of the repeating coil R to the conductor 31. Upon the closure of the above bridge, the line switch in which the conductors 30 and 31 terminate is operated in the usual and well known manner to extend the connection-to an idle first selector switch in the main exchange, whereupon the line relay of'such selector becomes energized over the conductors 30 and 31 in series. Although the lower winding of relay 22 at the repeater is included in this circuit, the energizing effects of the two windings of this relaynow oppose each other and it is not energized.

The foregoing operations have occurred in res onse to the insertion of the plug in the jac J. The operator will now throw her key K, with the result that the calling device CD is substituted for the polarized relay 4 in the previously described circuit of the relay 20., The calling device CD is now operated in accordance with the first digit of the desired number, thereby causing a number of deenergizations of the said relay 20 by producing a series of interruptions in its circuit. At each deenergization, relay 20 opens the bridge across the conductors 30 and 31 at its lower armature, thereby producing in the well known manner a series of deenergizations of the line relay of the first selector switch. The first selector is accordingly operated in the well -known manner to select and connect with a trunk line extending to an idle second selector switch associated with the desired main group of subscribers lines in the main exchange. Additional operations of the calling device will now be effective to bring about the operation of the selected second selector and a connector switch to complete the connection to the line of the called subscriber, the interruptions produced by the calling device being repeated to the line relays of these switches by the relay 20 of the repeater as before. The called subscriber is then signaled automatically from the connector switch in the usual manner.

Having called all the digits in the wanted number, the operator will restore her key K to normal position thereby cutting out the calling device CD and again inserting the olarized relay 4 in the circuit of relay 20. When the called subscriber responds by removing his receiver, the usual answering bridge in the connector is operated to reverse the direction of current flow in the conductors 30 and 31. By this operation the lowerwinding of 'relay 22 is energized in the proper direction to assist the upper windingand the said relay 22 is therefore operated. As a result a circuit is closed for the slow acting relay 23, which is so adjusted that its lower armature engages its working contact before its upper armature breaks away from its resting contact. The attraction of the lower armature of relay 23 closes a shunt path around the contact controlled by the lower armature of relay 20, and ,the foregoing adjustment is necessary in order to prevent relay 22 from being deenergized when the rela 20 falls back momentarily, due to the s ifting of its circuit at the upper armature of relay 23. By this latter operation, the upper terminal of relay 20 is disconnected from ground G and is connected instead to the resistance 24. Current now flows in the simplex control circuit as follows: ground at G, battery B resting'contact of the armature of the polarized relay 4 and the said armature, winding of relay 4, contact springs 8 and 7, contact springs 6 and 5 righthand windings of the repeating coil R in parallel, conductors 15 and 16 in parallel, lefthand windings of the repeating coil R in parallel, winding of relay 20, upper armature of relay 23 and its working contact, resistance 24, booster battery B and the battery B to ground G The above circuit it will be observed, is similar to the one previously of the inclusion of batteries B and B in the circuit, the direction of current flow is reversed The polarized relay 4 is now operated to remove the short circuit previously existing around the supervisory s1gnal 3, whereupon the signal is operated to notify the operatorv that the called subscriber has answeredi 'changeare' ,now connected in-opposition visory signal j of. this latte switches, of the rotar' exchange battery willbef'charged during con-- 'versation. Y

ment of thei rece'iyer atu-the called substation being efiectiveiito; give th ea disconnect signaljas fol-- answering ibridge at -jthe connector deener-r gizes and reversesj the' current in. the conductors '30 airildfil back t0-nOrmal, The'electropolarized;-"-'relay '22 zis then -,deenergized,

followed by the deene'rgization of "the slow.

acting [relay 1 Thef'ori circuit of relay."20fis there y'restored; an

' the polarized grela'y 4 at the branch exchange is operated to-again short circuit the 'sup'er F'by the deenergization1 eioperato'r is notified that 7 mentarg'et or other visual device disconnection tionedthatithe controlled {by "the supervisoryv magnet 3 should be arranged-preferably so 5 as to be visible l w he n the magnet is deenergized. Upon receiving the signal-,' the o erator will take down her cord circuit there yfbreaki'ng the energizing. circuit of the relay '20 "at"; the main exchange.','By the 'deener'gizationf resulting .deenergiz'ation': of relay'21 the bridge across the'trunkjcon 45 d of relay 20 and the uctors 30 and 31 is permanently opened (whether the, called I his receiver or 'not) and the automatic switches involved the connection are ac? cordingly released.-as usual..----,, -V w The establishment of ating at the main exchangeinvolves nothing switch in which the conductors; 30 and 31,

terminate are accessible. to connector type-,-" although they may be (similar to t e? connector switch shown in the above patent are assigned a telephonenumber. exchange subscriber then by callin ephone number is ableto establis connec-' tion to the trunk line extending to the branch A main exchange, whereupon the drop 2 at the latter point will be actuated by ringing current projected over the trunk nector switch. The operator' will answer I ,WhatI -Since the twobatteries-at the-main exr I connecting a branch exchan the 'batteiyj'at" the branch exchange, and: since together they are of greater electro-;-- motivejl'force, it is evident thatfthebranch for operating switches (to establish a connection between the branch v exchange and a subscriber in the main ex- When thesubscribers are through talking} they will replace their receivers, t e replace-- e operator at the nal --energiz"ing exchange and a change, a' battery s eqiineeiion origin? v q operating switches in new. The normal conductors of the-l1neto Newforth, and

this 1361- f line from the con change,- a battery in branch I exchange switches,

said circuit a at the main extion. l H

2.111 a telephone system, connecting a branch exchange with an automaticimain exchange, a switch control'circuitincluding a conductor. of said trunk for operating switches in the main exchan to establish a connection between the branch exchange and a change, a battery in saidcircuitrat the branch exchange,

battery tion. 3. In atelephone system, a trunk circuit connecting. a branch exchange with an automatic main exchange, a SWllZChcontrol circuit including aconductor of said trunk for operating switches in the main exchange to establish a. connection between the branch subscriber in the main exoversaid branch'exchange, and means controlled by a switch control cir-,

7t be pointed I in the main exchange for: controlling saidand means for. automatically" 7 charging said battery from the change over said circuit during conversaa trunk circuit subscribervinithe mainexand. means at the main exchange-for automatically chargingsaid circuitduring 'conversain said circuit at the the response of the called subscriber for au- I tomatically charging said battery durin' subscriber has replacedconversation.

change, a battery in said circuit at the saidbranch exchange for controlling 4. In a telephone system, a trunk'circuit connecting a branchexchange with an automatic main exchange, a switchcontrol cirswitchesover said circuit, and meanslat the main exchange including-a second battery of highervolta'ge than the said first battery 'cuit including a conductor of said trunk or: automatically charging the latter over for ope-rating switches in the main exchange to establish a connection between the branch exchange and a subscriber in the main exchange, a battery in said circuit at the branch exchange, means at the main exchange for automaticall charging said battery over said circuit uring conversation, and a supervisory rela at the branch exchange included 1n sai circuit and responsive to the reversal of current therein during the chargin operation.

6. In a te ephone system, a trunk circuit connecting a branch exchange with an automatic main exchange, a switch control circuit including a conductor of said trunk for operating switches in the main exchange to establish a connection between the branch exchange and a subscriber in themain exchange, a battery in said circult at the branch exchange, means controlled by the response of the called subscriber for automatically charging said battery during conversation, and a supervisory relay at the branch exchange included 1n said circuit and responsive to the reversal of current therein during the charging operation.

7. In a telephone system, a trunk circuit connecting a branch exchange with an automatic main'exchange, a switch control circuit including the two conductors of said trunk in parallel for operating switches in the main exchange to establish a talking connection, a battery in said circuit at the branch exchange, and means for automatically charging said battery from the main exchange over said circuit after the connection is established.

'8. In a telephone system, a trunk circuit connecting a branch exchan e with an automatic main exchange, a switch control circuit including the two conductors of said trunk in parallel for operating switches in the main exchange to establish a talking connection, a battery in said circuit at the branch exchange, and means at the main exchange for automatically charging said battery over said circuit during conversa- 9. In a telephone system, a trunk circuit connecting a branch exchange with an automatic main exchange, a switch control circuit including the two conductors of said trunk in parallel for operating switches inv 10. In a telephone'system, a trunk circuit connecting a branch exchange with an au tomatic main exchange, a switch control circuit including the two conductors of said trunk in parallel for operating switches in the main exchange to establish a talking connection, a battery in said circuit at the branch exchange, and means at the main exchange including a second battery of higher voltage than the said first battery for automatically charging the latter over said circuit after the connection is established.

11. In a telephone system, a trunk circuit connecting a branch exchange with an automatic main exchange, a switch control circuit including the two conductors of said trunk in parallel for operating switches in the main exchange to establish a talking connection,'a battery in said circuit at the branch exchange, means at the main exchange for automatically charging said battery over said circuit during conversation, and a supervisory relay at the branch exchange included in said circuit and response to the reversal of current therein during the charging operation.

12. In a telephone system, a trunk circuit connectinga branch exchange with an automatic main exchange, a switch control circuit including the two conductors of said trunk in parallel for operating switches in the main exchange to establish a talking connection, a battery in said circuit at the branch exchange, means controlled by the response of the called subscriber for automatically charging said battery during conversation, and a supervisory relay at the branch exchange included in said circuit and responsive to the reversal of current therein during the charging operation.

13. In a telephone system, a trunk line 100 connecting two exchanges, means including said trunk for establishing a talking connection between subscribers in the respective exchanges, a simplex circuit superimposed on said trunk and including the two conductors thereof in parallel, a supervisory relay in said circuit at one exchange, and means for controlling said relay from the other exchange by reversals of current produced in said circuit. I Y

14. In a telephone system, a trunk line connecting two exchanges, means including said trunk for establishing a talking connection between subscribers in the respective exchanges, a simplex circuit superimposed on said trunk and including the two conductors thereof in parallel, a supervisory relay and a battery in said circuit at one exchange, and means at the, other exchange comprising a second battery of higher voltage than the said first battery for producing a reversal of current in said circuit to operate said relay.

15. In a telephone system, a trunk line connecting-two exchanges, means including said trunk for establishing a talking connection between subscribers in the respec. tive exchanges, a simplex circuit superimposed on said trunk and including the two conductors thereof in parallel, a polarized supervisory relay at one exchange irresponsive to normal current flow in said circuit, and means at the second exchange including a second relay for reversing the direc tion of current flow in said circuit to operate said supervisory relay.

16. In a telephone system, a trunk'line connecting two exchanges, means including said trunk for establishing a talking connection between subscribers in the respective exchanges, a simplex circuit superimposed on said trunk and including the two conductors thereof in parallel, a supervisory relay in said circuit at one exchange, and means for controlling said relay from the other exchange upon the response of the called subscriber by, reversals of current produced in said circuit.

17. In a telephone system, an operators position and a trunk line extending therefrom, an automatic switch control circuit superimposed on said trunk line and including the two conductors thereof in parallel, a supervisory signal at the operators position, and means for reversing the direction of current flow in said circuit to control 1 said signal.

I cuit connectin 18. In a telephone system, a trunk cira branch exchange with an automatic main exchange, a switch control circuit including a conductor of said trunk for operating switches in the main exchange to establish a connection between the branch connecting a branch exchange with an automatic main exchange, a switch control circuit including the two conductors of said trunk in parallel for operating switches in the main exchange to establish a talking connection, a battery in said circuit at the branch exchange, a' source of current at the main exchange and automatic means for supplying said source by way of said cir;

cult to said battery to charge said batter after the talking connection is establishe 20. In a telephone system, a trunk circuit connecting a branch exchange with an automatic main exchan e, a switch control circuit including a con actor of said trunk for operating switches in the main exchange to establish a connection between the branch exchange and a subscriber in the main exchange, a battery in said circuit at the branch exchange, asource of current at the main exchange and automatic means for applying said source by way of said circuit to said battery to char e ,said battery when the main exchange subscriber answers.

21. In a telephone system, a trunk circuit connectin a branch exchange with an automatic main exchange, a switch control circuit including'the two conductors of said trunk in parallel for operating switches in the main exchange to establish a talking connection, a battery in said circuit at the branch exchange, a source of current at the main exchange and automatic means for supplying said source by way of said circuit to said battery to charge said battery when the main exchange subscriber answers.

22. In a telephone system, a trunk circuit connecting a -branch exchange with an automatic main exchange, a switch control circuit including a conductor of said trunk for operating switches in the main exchange to establish a connection between the branch exchange and a subscriber in the main exchange, a battery in said circuit at the branch exchange, a source of current at the main exchange and a relay for applying said source by way of said circuit to said battery to charge said battery after a talking connection is established.

23. In a telephone system, a trunk' circuit connectin a branch exchange with an automatic main exchange, a switch control circuit including the two conductors of said trunk in parallel for operating switches in the main exchange tov establish a talking connection, a battery in said circuit at the branch exchange, a source of current at the main exchange and a relay for supplying said source by way of said circuit to said battery to charge said battery upon response of the called subscriber.

24. In a telephgne system, a trunk circuit connecting a branch exchange with an for operating switches in the main exchange to establish a connection between the branch exchange and a subscriber in the main exchange, a battery in said circuit at the branch exchange, a source of current at the main exchange and a relay for applying said source by way of said circuit to said battery to charge said battery when the main exchange subscriber answers.

25. In a telephone system,a trunk circuit connecting a branch exchange with an automatic main exchange, a switch control circuit including the two conductors of said trunk in parallel for operating switches in the main exchange to establish a talking connection, a battery in said circuit at the branch exchange. a source of current at the mainexchange and a relay for supplyin said source by way of said circuit to said battery to charge said battery when the main exchange subscriber answers.

Signed by me at Chicago, Cook County State of Illinois, this 6th day of June, 1917.

JOHN WICKS. 

